1 August 1943:
At 0700, departs Tarakan with a cargo of refined oil in a convoy consisting of KOKUYO and NICHIEI MARUs with an unknown escort.
2 August 1943:
At 1800, arrives at Balikpapan. Loads a cargo of crude oil.
17 September 1943:
Departs Balikpapan for Tarakan with 3,947-tons (about 538 barrels) of crude for further refining.
26 September 1943:
Arrives at Rabaul.
21 October 1943:
Departs Tarakan with a cargo of refined oil for Balikpapan.
24 October 1943:
At 1730 destroyer SANAE departs Balikpapan escorting NISSHO and KOKUYO MARUs bound for Palau.

26 October 1943:
At 0700 SANAE ceases escort.

31 October 1943:
At 0830, while en route to Rabaul, meets up with minesweeper W-26 that escorts her to Rabaul.
2 November 1943:
Destroyer UZUKI joins escort.
5 November 1943: - The Carrier Raid on Rabaul:
Simpson Harbor, Rabaul. CruDiv 4's ATAGO, MAYA and TAKAO, CruDiv 7's SUZUYA and MOGAMI and CruDiv 8's CHIKUMA arrive at Rabaul. About noon, while KOKUYO MARU is refueling ATAGO, the cruisers are attacked by 97 planes from Rear Admiral (later Admiral) Frederick C. Sherman's (USNA ’10) Task Force 38's USS SARATOGA (CV-3) and USS PRINCETON (CVL-23). ATAGO sustains three near-miss bombs dropped by Douglas SBD “Dauntless” dive-bombers from USS SARATOGA that kill 22 crewmen including her skipper hit by a bomb splinter while on the bridge. TF 38's planes also damage TAKAO, MAYA, CHIKUMA and MOGAMI, light cruisers AGANO and NOSHIRO and destroyers AMAGIRI and FUJINAMI.
KOKUYO MARU transfers 400 tons fuel oil to heavy cruiser CHIKUMA, before the cruiser departs.
6 November 1943:
At 0340 alomgside heavy cruiser MAYA transferring fuel from damaged cruiser.
9 November 1943:
Departs Rabaul en route to Kavieng in convoy O-802 consisting of tanker KOKUYO MARU and cargo ship TAJIMA MARU making 11 knots.
24 November 1943:
At 0600, departs Tarakan carrying a cargo of refined oil in a convoy consisting of KOKUYO and AZUMA MARUs (ex cargo). Shortly after departing the two ships collide, but little damage results to either.
26 November 1943:
At 1400, arrives at Balikpapan. Loads a cargo of crude oil.
30 November 1943:
At 0700, departs Balikpapan in convoy with tankers KENYO and AZUMA MARUs (ex cargo) escorted by subchaser CH-6 and another unknown vessel.
3 December 1943:
LtCdr (later Rear Admiral) Lawrence R. Daspit's (USNA ’27) USS TINOSA (SS-283) sights the convoy and makes an approach, but the convoy zigs and ruins the setup. Daspit fires three torpedoes "up the kilt" at AZUMA MARU with a cargo of 500 drums of aviation gasoline, 500 drums of normal gasoline and 6,000-tons of heavy oil. At 1947 (I), one hits and sets her afire. She slows, then settles lower in the water and drops out of the convoy.
USS TINOSA moves in on the surface, but AZUMA MARU opens fire with her deck guns and machine-guns. Daspit crash dives and closes to point blank range. At 2121, he fires three more torpedoes that blow up and sink AZUMA MARU at 06-34N, 131-40E. 50 crewmen including her Captain and 18 passengers are KIA. Captain Ara Tadashi (33) is promoted Rear Admiral, posthumously. The remainder of the convoy continues towards Palau.
4 December 1943:
Arrives at Palau at 1200. Departs for Truk shortly thereafter.
14 December 1943:
Arrives at Tokuyama. [NB dubious may have remained in Rabaul area]
E 17 December 1943:
Departs Tokuyama. [NB dubious may have remained in Rabaul area]
18 December 1943:
At 0630 destroyer MINAZUKI departs Kavieng, and at 0900 destroyer UZUKI departs Rabaul to meet KOKUYO MARU. Late that day the ships arrive at Rabaul.
23 December 1943:
At Rabaul supplies bunkers to oiler NARUTO and destroyer FUMITSUKI.
5 January 1944:
At 1245 storeship ARASAKI and KOKUYO MARU in position 04-04N 125-12E meets up with convoy NE-202 consisting of GENYO MARU being escorted by patrol boat PB-2.
7 January 1944:
At 1320 arrives at Balikpapan.
8 January 1944:
At 1700, departs Balikpapan loaded with crude oil in convoy "KU"consisting of oilers NIPPON and KOKUYO MARUs making 14 knots, escorted by destroyers SHIMAKAZE and HAYANAMI and by patrol boat No. 102 (ex-USS STEWART, DD-224) at the start of the journey. [3]
17 January 1944:
At 0430 arrives at Truk.
19 January 1944:
Departs Truk for Rabaul with cargo ship NANREI MARU escorted by destroyers NOWAKI, YAMAGUMO and MAIKAZE.
22 January 1944:
Arrives at Rabaul. Departs that same day for Kavieng with NOWAKI and MAIKAZE and subchaser CH-36.
25 January 1944:
Departs Kavieng for Truk with NOWAKI and MAIKAZE.
28 January 1944:
Arrives at Truk.
5 February 1944:
At 1600, departs Truk in a convoy consiting of KOKUYO, NICHIEI and KYOKUTO MARUs escorted by destroyers OITE, SHIMAKAZE and IKAZUCHI.
11 February 1944:
At 1300, arrives at Davao.
12 February 1944:
At 1240, departs Davao with only SHIMAKAZE as escort.
15 February 1944:
At 0907, arrives at Balikpapan. Loads a cargo of crude oil.
21 February 1944:
Departs Balikpapan for Palau in a convoy consisting of KOKUYO, NISSHO and KYOKUTO MARUs escorted by destroyers SHIMAKAZE and IKAZUCHI.
25 February 1944:
Off Mindanao, Phillipines. At 0100, KYOKUTO MARU in convoy with oiler NISSHO MARU is attacked by LtCdr (later Cdr) Victor B. McCrea's (USNA ’32) USS HOE (SS-258), acting on a code-breaker's ULTRA message. McCrea fires four torpedoes in a surface radar attack and gets two hits on KYOKUTO MARU at 05-38N, 126-00E that cause heavy damage. At 0220, McCrea fires all ten bow and stern torpedoes in a surface radar attack. He gets five hits that sink NISSHO MARU at 05-50N, 126-00E. Captain Tonomura Senzaburo (40) (former CO of ERIMO) and 37 crewmen are KIA. Tonomura is promoted Rear Admiral, posthumously.
The remainder of the convoy arrives at Davao later that same day.
29 February 1944:
Departs Davao.
2 March 1944:
Arrives at Palau. The convoy is dissolved.
4 March 1944:
Departs Palau for Saipan.
10 March 1944:
Departs Saipan for Palau with destroyers FUJINAMI and HAYANAMI.
13 March 1944:
Arrives at Palau.
18 March 1944:
Departs Palau for Tarakan, then to Balikpapan with HAMANAMI.
22 March 1944:
Arrives at Tarakan. Loads refined oil.
25 March 1944:
Arrives at Balikpapan. Loads a cargo of crude oil.
29 March 1944:
At 1840 departs Balikpapan in convoy bound for Palau via Davao consisting of tankers GENYO and KOKUYO MARUs together with destroyers HAYANAMI and HAMANAMI, likely kaibokan KANJU and initially patrol boat PB-102.
1 April 1944:
Arrives at Davao. Refuels heavy cruiser ATAGO. The ships did not go to Palau, presumably because of the 30-31 March air raids there.
2 April 1944:
Davao. Provisioned by auxiliary storeship KITAKAMI MARU.
4 April 1944:
From 0714 - 1140 undertakes a refuelling at sea training exercise with ATAGO.
8 April 1944:
Departs Davao in convoy with GENYO MARU escorted by destroyers HAMAKAZE, TANIKAZE, URAKAZE, HAYANAMI and HAMANAMI and kaibokan KANJU.
10 April 1944:
Arrives at Tarakan.
12 April 1944:
Departs Tarakan still in convoy.
14 April 1944:
Arrives at Balikpapan. Loads crude oil.
18 April 1944:
Departs Balikpapann in a convoy also consisting of tankers GENYO and YUHO MARUs, and gasoline tanker SUNOSAKI escorted by destroyers OKINAMI, TANIKAZE and URAKAZE and kaibokan KANJU.
26 April 1944:
Arrives at Saipan, Marianas. Discharges fuel oil.
29 April 1944:
Departs Saipan in convoy also consisting of tankers GENYO and YUHO MARUs, and gasoline tanker SUNOSAKI escorted by destroyers OKINAMI, TANIKAZE and URAKAZE and kaibokan KANJU.
7 May 1944:
At 1100 arrives at Balikpapan. Loads fuel oil.
13 May 1944:
At 0800 departs Balikpapan in a convoy also consisting of GENYO MARU and gasoline tanker SUNOSAKI escorted by destroyer TANIKAZE and URAKAZE.
15 May 1944:
At 1135 arrives at Tawi Tawi.
17 May 1944:
At 1728 begins refuelling heavy cruiser KUMANO, until 2113.
23 May 1944:
At 0640, departs Tawi Tawi in a convoy consisting of KOKUYO, NICHIEI, SEIYO and TATEKAWA MARUs escorted by destroyers HIBIKI, AKISHIMO and HAMAKAZE.
24 May 1944:
Off Saranagani Islands, Mindanao. In the early afternoon, lookouts aboard LtCdr Charles H. Andrews' (USNA ’30) USS GURNARD (SS-254) sight a convoy they identify as consisting of two oilers, "two cargo ships" and three destroyers. Slipping past the escorts, Andrews fires four torpedoes at an oiler. At 1517 TATEKAWA MARU is hit by two torpedoes, the first in oil tank No. 6 and the second in the engine room. She is set ablaze. Ten of her armed guard gunners and 17 crewmen are killed. TATEKAWA MARU sinks at 05-45N, 125-43E E.
25 May 1944:
At 0200, arrives at Davao.
27 May 1944: American Operation “Horlicks” – The Invasion of Biak:
Rear Admiral (later Admiral) William M. Fechteler’s (USNA ’16) Task Force 77 lands Maj Gen Horace H. Fuller’s 41st Division on Biak off New Guinea.
13 June 1944: Operation A-GO - The Defense of the Philippines.
Davao. Battleship FUSO transfers fuel oil to the 1st Supply Force’s oilers KOKUYO, NICHIEI and SEIYO MARUs and HAYUSUI.
14-15 June 1944:
Departs Davao for refuelling rendezvous with the Mobile Fleet. Enroute, about 90km SE of Surigao Strait, SEIYO MARU collides with and sinks destroyer SHIRATSUYU at 09-09N, 126-51E with the loss of 104 sailors including her CO, LtCdr Matsuda Kuro (55), promoted Captain posthumously.
16 June 1944:
At about 1000, at 11-00N, 130-00E, the 1st Supply Force's oilers HAYUSUI and NICHIEI, KOKUYO and SEIYO MARUs rendezvous with Vice Admiral Ugaki Matome's (40) (former CO of HYUGA) aborted Operation "Kon" Task Force's Bat Div 1's YAMATO and MUSASHI, Cru Div 5's HAGURO and MYOKO, DesRon 2's light cruiser NOSHIRO and Des Div 4's OKINAMI, SHIMAKAZE, ASAGUMO, MAIKAZE and MICHISHIO and DesRon 10's YAMAGUMO and NOWAKI.
Ugaki's force is refueled promptly, then Ugaki's force and the 1st Supply Force head north to join Vice Admiral Ozawa Jisaburo's (37) (former CO of HARUNA) First Mobile Fleet's Main Body. At 1650, they rendezvous with Ozawa. The 1st Supply Force begins to refuel the Mobile Fleet. At 2310 begins refuelling cruiser TAKAO.
17 June 1944:
At 0150 completes refuelling TAKAO. KOKUYO MARU then refuels CruDiv 7's TONE (at 0734 with 397 tons) and SUZUYA. By 2000, refueling of the First Mobile Fleet's Main Body is completed. At this time, the First Mobile Fleet is at 12-15N, 132-45E. The 1st Supply Force stands by to rendezvous with the 2nd Supply Force's oilers GENYO and AZUSA MARUs enroute from Guimaras. All six oilers then depart the area for a designated standby point at 14-40N, 134-20E.
20 June 1944: Operation A-GO - The Battle of the Philippine Sea:
The Supply Forces are attacked by LtCdr J. D. Blitch's seven Grumman "Avenger" TBF torpedo-bombers, 12 Curtiss "Helldiver" SB2C dive-bombers and 16 "Hellcat" F-6F strafers from Task Force 58's USS WASP (CV-18). HAYASUI is hit by a bomb and set afire. SEIYO (three crewmen KIA) and GENYO MARU (apparently no casualties) are damaged by bombs and later scuttled by destroyers.
KOKUYO MARU departs the Philippine Sea for Okinawa.
23 June 1944:
Arrives at Okinawa. Refuels the Mobile Fleet for its return to Japan. Departs Okinawa the same day via Manila to Singapore with destroyers FUJINAMI and TAMANAMI.
29 June 1944:
Arrives at Singapore.
2 July 1944:
Departs Singapore for Manila with FUJINAMI and TAMANAMI.
7 July 1944:
South China Sea. At about 0200, while enroute to Manila, TAMANAMI is hit by three torpedoes fired by LtCdr Joseph J. Staley's (USNA ’34) USS MINGO (SS-261) and sinks bow first at 14-10N, 117-50E with all hands, including Comdesdiv 32 (Commander Aoki Kyuji (50).
23 July 1944:
At 1325 KOKUYO MARU suffers an engine breakdown in Manila Bay but is able to resume voyage at 1340.
24 July 1944:
At 1340 at Manila refuels destroyer YUZUKI.
July 1944:
Departs Manila in ballast for Macassar, Celebes.
30 July 1944:
125 miles W of Jolo. At about 0100, KOKUYO MARU which is being escorted by kaibokan CD-22 and submarine chasers CH-30 and CH-33 en route from Manila to Balikpapan and Macassar, is attacked by LtCdr (later Cdr) Lawrence L. Edge's (USNA ’35) USS BONEFISH (SS-223). Hit by four of five torpedoes Edge fires in a night surface radar attack. Blows up and sinks by the stern at 06-03N, 120-00E. Nine crewmen are killed. [4]
10 September 1944:
Removed from the Navy List.
Authors' Note:
[1] CarDiv 1's KAGA was in dock at Sasebo at the time.
[2] Hawaiian Time.
[3] Records show KOKUYO MARU was the only survivor of a fast tanker convoy that left Balikpapan on 8 Jan '44. Since the ship was capable of 19 knots empty versus 11 knots for the slowest ship in the convoy (AKIBASAN MARU), it is probable that KOKUYO MARU split from the convoy, probably at Saipan, and made her way to Balikpapan since only a laden tanker would sail to Truk and Rabaul.
Alternatively, it is possible that the KOKUYO MARU concerned was the warbuilt 43 4667 cargo ship, although the kanji for this ship is different from the vessel in convoy 3231.
[4] LtCdr Edge and USS BONEFISH were lost later in the war.
Thanks for assistance goes to Allan Alsleben of Oregon and Mr. Gilbert Casse of France.
Photo credit goes to Ron Wolford via Gilbert Casse.